Im playing with the vanilla resources, i think the faster and extremely fast belts and underground belts are too cheap compared to normal>fast>express. Currently they only cost a few more gear wheels. I tend to skip faster belts for this reason. They should require an extra item like steel plates (realistically to make them sturdier), and some more lube.

I suggest:

Faster belt: 1x express belt, 5x iron gears + 2x steel plates
Extremely fast belt: 1x faster belt, 5x iron gears + 2x lubricant

Faster underground belt: 1x express underground belt, 20x iron gears + 10x steel plates
Extremely fast underground belt: 1x faster underground belt , 20x iron gears + 10x lubricant

Try to play with Bob's Ores. With ores it requires Titanium which is quite rare, especially with RSO.

Too many different ores for me, i don't like it.